An investigation has begun into the death of a man in police custody in Devon, the police watchdog has said.
Simeon Francis, 35, who was black, died in a cell in Torquay police station on 20 May after being arrested in Exeter, the Independent Office for Police Conduct (IOPC) said.
A preliminary post-mortem examination did not find a cause of death, it said.
Devon and Cornwall Police said it was "co-operating fully" with the independent inquiry.
Mr Francis was arrested at about 00:45 BST on 20 May in Cowley Bridge Road in Exeter. He was transported by van to Torquay before being booked into custody at about 03:00, the IOPC said.
Police said paramedics were called after he was found "seriously unwell" in his cell in the afternoon. The IOPC said an ambulance crew pronounced him dead at about 18:00.
The investigation followed a mandatory referral from the Devon and Cornwall force, which officers announced the day after the death.
Regional IOPC director Catrin Evans said: "Our thoughts are with Mr Francis's family and friends following his death."
She said investigators were gathering evidence and statements from officers and "analysing a considerable amount of CCTV footage from the custody suite".
She said: "We are looking at the level of care provided during the period of detention, including the frequency and adequacy of checks carried out."
Further tests were also to be carried out on Mr Francis's body, she said.